Startup Devises Liquid Metal Batteries for the Electricity Grid

A Boston-area startup has invented new liquid-based heavy-duty battery technology that its founders hope will be the foundation of the next-generation electricity grid in which alternative energy will play a key role. Ambri -- yet another company formed out of that bastion of modern invention, the Massachusetts Institute of Technology (MIT) -- is developing giant cells that are comprised of liquid electrodes and an electrolyte capable of storing large amounts of solar and wind power at a low cost.

The battery is the brainchild of Donald Sadoway and Ambri CTO David Bradwell, co-founders of the company that developed the technology at MIT in the lab of Sadoway, a professor of materials chemistry there.

As Sadoway explained last year at a TED conference -- a talk posted in a video on the company’s website -- he worked for about six years to come up with a battery chemistry that could meet the intensive needs of the power industry, which are “uncommonly high power, long service lifetime, and super-low cost.”

David Bradwell (left) and Donald Sadoway are co-founders of Ambri, a Cambridge, Mass.-based startup that is developing a liquid-based battery they hope will be the foundation for the next-generation electricity grid. (Source: MIT)

“With a giant battery, we could address the problem of intermittency that prevents wind and solar from contributing to the grid in the same way that coal and gas and nuclear do today,” Sadoway said. “The battery is the key enabling device here. With it we could draw electricity from the sun when the sun doesn’t shine.”

He employed Bradwell -- then a post-doc at MIT -- to create the battery from his concept of using metals that when heated form liquids that are the basis for the battery, using a low-density liquid metal at top, a high-density liquid metal at bottom with a layer of molten salt in between as the electrolyte. The first battery created by Sadoway and Bradwell used magnesium at the top as the negative electrode and antimony at the bottom as the positive electrode.

The chemistry works like this: When the battery discharges power, magnesium atoms give off electrons that travel through the salt layer and react with the antimony. This forms an alloy and expands the bottom layer of the cell, or the cathode. To charge, the battery itself acts like a metal smelter, separating the magnesium from its alloy back through the electrolyte to return to the magnesium. In this way, too, the battery self heats, which keeps the metals liquid.

Ambri has since started using less expensive and higher voltage metals and salt for the battery, but it continues to work in the same way, according to the company. Eventually the cells will be stacked into modules the size of 40-ft shipping containers with “the nameplate capacity of two megawatt-hours -- 2 million watt-hours,” Sadoway said. “That's enough energy to meet the daily electrical needs of 200 American households,” he said. “So here you have it, grid-level storage: silent, emissions-free, no moving parts, remotely controlled, designed to the market price point without subsidy.”

Ambri is not the only company that’s invented new technology that could allow energy generated by wind and solar sources to take a more central role in the utility grid. Automation vendor ABB said recently it had solved a longtime problem of how to transport power over long distances with the design of the first circuit breaker for high-voltage direct current, or HVDC. This would allow for connections between large wind farms and solar power grids from different places to be plugged into the traditional power grid, the company said.

Just a thought, but if the water "siting" was inside a sealed enclosure, only opened when necessary, would hydro be a better option? The size of the container to enclose a lake might be a bit sci-fi though...

What could be reasonable for bulk energy storage in fixed locations is good old lead batteries, since the lead is a common metal and fairly simple to recycle, and the technology is quite well understood. That is a bunch of reasons to consider a tecnology not right at the cutting edge.

I was thinking exactly the same issues... But wandered a little aroud the thermodynamics of it: any heating (self heating) would represent a form of looses (like heating from mechanical friction or self heating by eddy currents in transformer cores)... And heating looses would raise inefficiency. Measuring some NiMH and LiPo's batteries for my R/C model airplanes with a good intelligent charger, reveals batteries have quite different values between energy charged (In) vs. energy delivered (out), but I seldom see discussions on this inefficiency, and no thermal insulation is perfect. In some cases, even dedicating some energy to maintain cooler Battery temperatures by using extra fans (driven from the same battery) is advantageous, but costs more energy wasted to keep the battery from melting itself. [high power electrical powered model airplanes with several horsepower motors].

Exactly. Major problem there...evaporation and other water retention problems. Other issues come in the loss of power through the inefficient pumps and other electrical mechanisms. Not to mention the reconversion of the water back to electricity through turbines.

The battery cuts out a lot of the problems of other systems, cuts right to the chase, electrical power ready to go.

When you say "water displacement," Cabe, are you referring to pumped hydro? Pumped hydro -- pumping water up to a higher spot and then using it to spin a generator -- is still the most common form of grid storage by far, I believe.

I know many are making batteries for storage already, but as I said, cost is high. Especially compared to old methods like water displacement. I also read about freezing, momentum, and weight storage of energy. All of which seemed silly.

Perhaps when capacitors reach higher density of surface area, they could be used.

Yes, the known reserves of Antimony (Sb) are less than 2M tonnes. That may sound like a lot but antimony, like lead, is very heavy so those "40 foot containers" might contain as much 20 tonnes each. Worse yet, the huge percentage of antimony reserves are in China - which has recently shown a reluctance to expolit their rare-earths further than 2010 levels.

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